Jet Physics at LEP and World Summary of ${\alpha }_s$

Abstract

Recent results on jet physics and tests of QCD from hadronic final states in $e^{+}{e}^{-}$ annihilation at PETRA and at LEP are reviewed, with special emphasis on hadronic event shapes, charged particle production rates, properties of quark and gluon jets and determinations of ${\alpha }_s$. The data in the entire energy range from PETRA to LEP-2 are in broad agreement with the QCD predictions. The world summary of measurements of ${\alpha }_s$ is updated and a detailed discussion of various methods to determine the overall error of ${\alpha }_s(M_Z)$ is presented. The new world average is ${\alpha }_s(M_Z)=0.119\pm 0.004$. The size of the error depends on the treatment of correlated uncertainties.

Comments: Talk presented at the $I{V}^{th}$ Int. Symp. on Radiative Corrections, Barcelona, Sept. 8-12, 1998. 18 pages, 13 eps-figures; uses sprocl.sty and psfig.sty